Elements, Compounds and Moxtures

• any substance that is made of only one type of atom is an element
• Different types of atoms can combine chemically in many different ways to form compounds.
• Elements or compounds can also be mixed together physically in many different ways to form different mixtures
• Definition of an element

  An element is a pure chemical substance that cannot be broken down into two or more simpler substances by chemical processes
• Diatomic Elements

  • Have (Hydrogen)
  • No (Nitrogen)
  • Fear (Fluorine)
  • Of (Oxygen)
  • Iced (Iodine)
  • Cold (Chlorine)
  • Beer (Bromine)
• Definition of Compound


  A compound is a pure chemical substance formed when two or more elements are chemically combined in a fixed ratio to form a new product
• Definition of Mixture


  A mixture contains two or more components (elements or compounds) mixed together in any proportion.
• Mixtures vs Compounds (mixture)


  A mixture can be separated into its constituents by physical processes (filtration, evaporation, sublimation, distillation)
• Mixture vs Compounds (compounds)


  A compound cannot be separated into its constituents by physical processes. It can only be separated by chemical means.
• Mixture vs Compounds (mixture)


  A mixture shows the properties of its components
• Mixture vs Compounds (compounds)


  A compound has a new set of properties different from its elements
• Mixture vs Compounds

  Components of a mixture vary and the constituents are present in any proportion by weight. It does not have a definite formula while a compound has a fixed formula and composition.
• Mixture vs Compounds (mixture)


  In a mixture, the constituents do not react chemically thus no energy changes take place
• Mixture vs Compounds (compounds)


  In a compound, chemical reactions take place and energy changes in the form of heat and light are involved.
• Mixture vs Compounds (mixture)


  A mixture does not have a sharp melting point and boiling point
• Mixture vs Compounds (compounds)


  A compound has a sharp melting point and boiling point
• Mixtures are classified into homogeneous and heterogeneous

  Heterogeneous mixtures consists of two or more components that do not mix well with each other (eg. water and oil)
• Mixtures are classified into homogeneous and heterogeneous


  Homogeneous mixtures consist of two or more components that mix well with each other (usually are transparent; eg. sugar and water)
• Solution vs Suspension

  Solutions are clear and allow light to pass through it. The tiny particles of the solute are too small to reflect or block any light passing through the solution
• Solution vs Suspension

  When a solution is left to stand, it does not separate from the solvent
• Solution vs Suspension

  A suspension is usually cloudy as light cannot pass through it. The insoluble particles are large enough to block light passing through it
• Solution vs Suspension

  When a suspension is left to stand for some time, the insoluble particles will float on top or settle to the bottom
• Solution vs Suspension

  When a solution is filtered, no residual particles retain on the filter paper.
• Solution vs Suspension

  Since the insoluble particles are large, when a suspension is being filtered, there will be some particles left behind on the filter paper as residue when the it is filtered
• Suspensions are not clear and not transparent

  Solutions are clear and transparent.
• What are the main factors that affect solubility?

  • nature of the solute and solvent
  • physical state of the solute (eg. liquid or gas)
  • temperature
• Factors determining how fast a substance dissolves

  • size of the particles
  • amount of solute already dissolved
  • temperature
• Factors determining how fast a substance dissolves (Size of the particle)

  When a solute dissolves, the action only takes place at the surface of each particle. When the total surface area of the solute particles is increased, the solute dissolves more rapidly. Breaking a solute into smaller pieces increases its surface area and hence its rate of solution dissolving.
• Factors determining how fast a substance dissolves (Amount of solute already dissolved)

  When there is little solute already in the solution, dissolving takes place relatively rapidly. As the solution approaches the point where no solute can be dissolved, dissolving takes place more slowly
• Factors determining how fast a substance dissolves (temperature)


  For liquid and solid solutes, increasing the temperature not only increases the amount of solute that will dissolve but also increases the rate at which the solute dissolves. For gases, the reverse is true. An increase in temperature decreases both solubility and rate of diffusion.